In the normal manufacture of two-piece containers such as drinking cups and food tubs from paper or cardboard sheet, there are a number of disadvantages which are inherent in this material even though the material readily adapts itself to higher machine speeds in view of the fact that it will lie flat on a carrier in the machine, is readily deformable and holds printing very well. Also, polyethylene coated on paper can be utilized so as to provide a heat sealed seam in the sidewall of the container and around the bottom curl of the container. Normally, without such laminations, however, single sheets of material are either too expensive or do not have satisfactory heat sealable characteristics. Paper and cardboard materials, both coated and uncoated, suffer from wicking at the cut edges of the side seam such that if liquid or liquid containing foods are placed within such containers, there is a general deterioration of the side seam edge. Furthermore, such two-piece containers in the past have been usable for alcoholic beverages in the case where wicking is prevalent or sealing the paper or cardboard sheet with was is necessary in the general manufacture of such containers since the alcohol destroys the wax seal.
Accordingly, there is a need in the art for containers of material which print, form and handle like paper but which have the following additional characteristics;
1. High resistance to penetration by grease and resistance to moisture;
2. Do not wick at cut edges such as at the side seam;
3. Are thermoformable, and preferably, upsettable and flowable to form substantially solid seams by heat sealing;
4. Can be preprinted like paper containers prior to forming;
5. Form like paper into containers from flat blanks at substantially high machine speeds;
6. Have the capability of being provided with a mat or gloss finish selectively;
7. Are heat sealable; and
8. Can be used without additional coating materials such as a layer of wax or polyethylene without being damaged by alcoholic beverages, hot beverages or the like.
It is therefore an object of the present invention to provide a new and novel two-piece container for drinking cups and food cups.
It is another object of the present invention to provide a new and novel method of manufacturing two-piece drinking cups and food cups.
Still another object of the present invention is to provide a new and novel heat sealed thermoplastic two-piece drinking cup and food cup structure.
Yet another object of the present invention is to provide new and novel method and means for forming uniform liquid tight heat sealed seams in thermoplastic sheet materials.
Yet another object of the present invention is to provide a method and means for manufacturing two-piece thermoplastic containers such as drinking cups and food cups from filled thermoplastic sheet material on substantially conventional container making equipment.
These and other objects of the present invention will become more fully apparent with reference to the following specification and drawings which relate to a preferred embodiment of the present invention.